CVE-2020-8194 Overview
CVE-2020-8194 is a reflected code injection vulnerability affecting Citrix Application Delivery Controller (ADC), Citrix Gateway, and Citrix SD-WAN WANOP appliances. This vulnerability allows attackers to modify file downloads through a code injection attack vector that requires user interaction. The flaw exists in multiple firmware versions across the affected product lines, potentially enabling attackers to compromise the integrity of files downloaded by users through these network appliances.
Critical Impact
Successful exploitation allows attackers to inject malicious code that modifies file downloads, potentially leading to malware distribution, supply chain compromise, or credential theft through tampered downloads.
Affected Products
- Citrix Application Delivery Controller Firmware (versions before 13.0-58.30, 12.1-57.18, 12.0-63.21, 11.1-64.14, 10.5-70.18)
- Citrix Gateway Firmware (versions before 13.0-58.30, 12.1-57.18, 12.0-63.21, 11.1-64.14, 10.5-70.18)
- Citrix NetScaler Gateway Firmware (affected versions)
- Citrix SD-WAN WANOP (versions before 11.1.1a, 11.0.3d, 10.2.7)
- Citrix 4000-WO, 4100-WO, 5000-WO, 5100-WO Appliances
Discovery Timeline
- July 10, 2020 - CVE-2020-8194 published to NVD
- November 21, 2024 - Last updated in NVD database
Technical Details for CVE-2020-8194
Vulnerability Analysis
This vulnerability is classified under CWE-94 (Improper Control of Generation of Code), commonly known as Code Injection. The flaw resides in how the affected Citrix products handle certain input parameters, allowing attackers to inject malicious code that gets reflected back to users. Unlike persistent code injection, this reflected variant requires the victim to interact with a malicious request, such as clicking a crafted link.
The vulnerability specifically impacts the file download functionality of the affected appliances. When exploited, an attacker can manipulate the download process to serve modified or malicious files to end users. This is particularly concerning given that Citrix ADC and Gateway appliances are typically deployed at network perimeters and handle significant amounts of enterprise traffic.
The attack requires network access and user interaction, meaning victims must be tricked into clicking a malicious link or visiting a compromised page that triggers the vulnerable functionality.
Root Cause
The root cause stems from insufficient input validation and improper sanitization of user-controllable parameters within the file download handling mechanism. The affected components fail to properly neutralize special elements that could be interpreted as code, allowing injection of arbitrary content that modifies the behavior of file downloads.
Attack Vector
The attack is network-based and requires user interaction to succeed. An attacker would typically:
- Craft a malicious URL or request containing the injected code payload
- Deliver this payload to a victim through phishing, watering hole attacks, or other social engineering techniques
- When the victim interacts with the malicious request, the injected code executes in the context of the Citrix appliance
- The resulting file download is modified, potentially containing malware or malicious scripts
The network attack vector combined with the requirement for user interaction means that while the vulnerability is remotely exploitable, it requires some degree of social engineering to achieve successful exploitation.
Detection Methods for CVE-2020-8194
Indicators of Compromise
- Unusual HTTP request patterns to Citrix ADC/Gateway management interfaces containing encoded or obfuscated payloads
- Unexpected modifications to file downloads passing through Citrix appliances
- User reports of corrupted or suspicious downloads from applications behind Citrix infrastructure
- Web server logs showing requests with injection-style payloads targeting download functionality
Detection Strategies
- Implement web application firewall rules to detect and block code injection patterns in requests to Citrix appliances
- Monitor for anomalous request patterns targeting known vulnerable endpoints on Citrix ADC and Gateway devices
- Deploy network traffic analysis to identify potential exploitation attempts containing reflection payloads
- Enable comprehensive logging on Citrix appliances and forward logs to SIEM for correlation and analysis
Monitoring Recommendations
- Configure alerting for HTTP requests containing potential code injection payloads to Citrix management interfaces
- Implement file integrity monitoring for downloads passing through Citrix appliances to detect unauthorized modifications
- Monitor authentication logs and access patterns for signs of post-exploitation activity
- Review Citrix appliance configurations regularly for unauthorized changes that may indicate compromise
How to Mitigate CVE-2020-8194
Immediate Actions Required
- Identify all Citrix ADC, Gateway, and SD-WAN WANOP appliances in your environment and verify firmware versions
- Apply the appropriate security patches immediately for all vulnerable systems
- Review access controls and ensure management interfaces are not exposed to untrusted networks
- Implement network segmentation to limit potential attack surface
Patch Information
Citrix has released security patches addressing CVE-2020-8194. Organizations should upgrade to the following versions or later:
- Citrix ADC and Gateway: 13.0-58.30, 12.1-57.18, 12.0-63.21, 11.1-64.14, or 10.5-70.18
- Citrix SD-WAN WANOP: 11.1.1a, 11.0.3d, or 10.2.7
Detailed patch information and download links are available in the Citrix Security Advisory CTX276688.
Workarounds
- Restrict access to Citrix management interfaces to trusted networks and IP addresses only
- Implement web application firewall rules to filter potentially malicious injection attempts
- Enable additional authentication mechanisms for accessing sensitive Citrix functionality
- Consider deploying a reverse proxy with additional security controls in front of Citrix appliances until patching can be completed
# Example: Restrict management interface access via Citrix CLI
# Limit access to trusted management network
add ns ip 192.168.1.100 255.255.255.0 -mgmtAccess ENABLED
set ns ip 192.168.1.100 -restrictAccess ENABLED
add ns acl MGMT_RESTRICT ALLOW -srcIP = 10.0.0.0-10.0.0.255 -destIP = 192.168.1.100
apply ns acls
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
